1. Field of the Invention
The present invention relates to a refrigerant suction side to liquid refrigerant heat exchanger located in such a way that the sensing bulb of a thermostatic expansion valve (TXV) whether mechanical or electronic, is located downstream of the heat exchanger, which is in turn downstream of the evaporator, in the direction of flow of the suction gas towards the compressor, so that the preset superheat setting of the thermostatic expansion device/valve is not exceeded by the action of the heat exchanger.
This invention more particularly pertains to the heat exchanger reducing or eliminating both the flash gas loss and superheat regions of an evaporator, thereby increasing the effective surface area of an evaporator and providing for a colder average temperature of the evaporator and providing for an increased mass flow of refrigerant through the evaporator and thereby an increased heat absorbing capacity of the evaporator.
Where the primary function of the refrigerant is to provide heat such as in a heat pump, pool heater or dedicated heat pump water heater, the overall coefficient of performance of the heat pump is dramatically increased in the evaporator efficiency improvement as well as by the heat reclaiming action of the heat exchanger of the heat contained in the liquid refrigerant.
2. Description of the Background Art
Presently there exist many types of devices designed to operate in the thermal transfer cycle. The vapor-compression refrigeration cycle is the pattern cycle for the great majority of commercially available refrigeration systems. This thermal transfer cycle is customarily accomplished by a compressor, condenser, throttling device and evaporator connected in serial fluid communication with one another. The system is charged with refrigerant, which circulates through each of the components. More particularly, the refrigerant of the system circulates through each of the components to remove heat from the evaporator and transfer heat to the condenser. The compressor compresses the refrigerant from a low-pressure superheated vapor state to a high-pressure superheated vapor state thereby increasing the temperature, enthalpy and pressure of the refrigerant. A superheated vapor is a vapor that has been heated above its boiling point temperature. It then leaves the compressor and enters the condenser as a vapor at some elevated pressure where the refrigerant is condensed as a result of the heat transfer to cooling water and/or to ambient air. The refrigerant then flows through the condenser condensing the refrigerant at a substantially constant pressure to a saturated-liquid state. The refrigerant then leaves the condenser as a high pressure liquid. The pressure of the liquid is decreased as it flows through the expansion valve causing the refrigerant to change to a mixed liquid-vapor state. The remaining liquid, now at low pressure, is vaporized in the evaporator as a result of heat transfer from the refrigerated space. This vapor then enters the compressor to complete the cycle.
The ideal cycle and hardware schematic for vapor compression refrigeration is shown in FIG. 1 as cycle 1-2-3-4-1. More particularly, the process representation in FIG. 1 is represented by a pressure-enthalpy diagram, which illustrates the particular thermodynamic characteristics of a typical refrigerant. The P-h plane is particularly useful in showing the amounts of energy transfer as heat. Referring to FIG. 1, saturated vapor at low pressure enters the compressor and undergoes a reversible adiabatic compression, 1-2. Adiabatic refers to any change in which there is no gain or loss of heat. Heat is then rejected at constant pressure in process 2-3, an adiabatic pressure change occurs through the expansion device in process 3-4, and the working fluid is then evaporated at constant pressure, process 4-1, to complete the cycle.
However, the actual refrigeration cycle may deviate from the ideal cycle primarily because of pressure drops associated with the fluid flow and heat transfer to or from the surroundings.
It is readily apparent that the evaporator plays an important role in removing heat from the thermal cycle. Evaporators convert a liquid to a vapor by the addition of heat extracted from the air or other material in contact with the evaporator. The evaporator surface area has three distinct zones; the flash gas loss area, where the liquid refrigerant is cooling adiabatically (no heat transfer theoretically) to the phase change temperature; the phase change area where the liquid refrigerant is evaporating because of heat being absorbed from the material the evaporator is in contact with and; the superheat region where all of the liquid has been evaporated and now the gas phase refrigerant is absorbing heat.
Both the flash gas loss region and the superheat region of the evaporator are less effective at removing heat than the phase change area. By reducing or eliminating both of these areas and increasing the area of phase change, the entire surface area of the evaporator becomes more effective in removing heat. In fact, the colder the refrigeration application the greater the effect of this elimination of the flash gas loss and superheat regions. The low pressure, suction side to liquid refrigerant heat exchanger, with the sensing bulb or sensor of a mechanical or electronic thermostatic expansion valve located downstream of the heat exchanger in the direction towards the compressor, accomplishes maximum subcooling by allowing sufficient excess refrigerant through the TXV to fully subcool the liquid refrigerant while maintaining the superheat setting of the TXV, thereby reducing or eliminating both the flash gas loss region and superheat regions of the evaporator.
There currently are known low pressure, suction side to liquid refrigerant heat exchangers where superheat above the TXV superheat set point is utilized to subcool the liquid refrigerant. The problem with these known heat exchangers are that this increased superheat temperature reduces the volumetric efficiency of the compressor, increases the hot gas discharge temperature, increases the operating temperature of the compressor thereby decreasing the operational life expectancy of the compressor and only minimally affects the liquid refrigerant temperature because of the limited effectiveness of using superheat only to cool the liquid refrigerant.
None of the known embodiments of the suction side to liquid refrigerant heat exchanger art deals with these known deficiencies that exist within the scope of this type of heat exchanger art.
In response to these realized inadequacies of earlier configurations of low pressure, suction side to liquid refrigerant heat exchangers used within the thermal transfer cycle of air conditioners, refrigeration equipment and heat pumps, it became clear that there is a need for a suction side to liquid refrigerant heat exchanger that would overcome these realized inadequacies. The result of the use of this new low pressure, suction side to liquid refrigerant heat exchanger system design being greater refrigeration capacity and improved dehumidification (for air cooling systems), both gained at relatively little additional power consumption for the total refrigeration thermal cycle. The greater capacity being realized from the higher mass flow of refrigerant through the evaporator due to improved evaporator heat exchange brought about by the reduction or elimination of the flash gas loss and superheat regions in the evaporator through the use of the new and improved low pressure, suction side to liquid refrigerant heat exchanger system. Further, in heating applications, in addition to the improved heat absorption effect on the evaporator, the low pressure, suction side to liquid refrigerant heat exchanger acts as a reclaimer for heat normally wasted in the flash gas region thereby providing even more heating capacity. Inasmuch as the art comprises various types of evaporator low pressure, suction side to liquid refrigerant heat exchangers, and condenser thermal transfer cycle configurations, it can be appreciated that there is a continuing need for and interest in improvements to evaporator low pressure, suction side to liquid refrigerant heat exchanger and condenser systems and their configurations, and in this respect, the present invention addresses these needs and interests.
Therefore, an object of this invention is to provide an improvement, which overcomes the aforementioned inadequacies of the prior art devices and systems and provides an improvement, which is a significant contribution to the advancement of the evaporator, suction side to liquid refrigerant heat exchanger and condenser system art.
Another objective of the present invention is to provide a new and improved low pressure, suction side to liquid refrigerant heat exchanger system, which has all of the advantages and none of the disadvantages of, the earlier low pressure, suction side to liquid refrigerant heat exchanger systems as utilized in a thermal transfer cycle.
Still another objective of the present invention is improved thermodynamic efficiency.
Yet another objective of the present invention is to provide maximum subcooling of the liquid refrigerant before entering the evaporator, through a thermostatic expansion valve, thereby reducing or eliminating the flash gas loss region of the evaporator.
An additional objective of the present invention is to provide maximum liquid refrigerant subcooling without exceeding the superheat setting of the thermostatic expansion valve.
Yet a further objective of the present invention is to minimize adverse affects to the compressor due to the low pressure, suction side to liquid refrigerant heat exchanger and evaporator system.
An additional objective of the present invention is to provide increased refrigeration capacity.
Still another objective of the present invention is to provide an apparatus and method that will increase overall refrigerant mass flow thereby increasing refrigeration capacity while doing so in a more efficient manner.
Another objective of the present invention is to allow for increased latent heat removal in air-cooling systems and therefore provide increased dehumidification.
And yet a further objective of the present invention is to reclaim normally wasted heat that occurs when warm liquid refrigerant cools down to the phase change temperature in the flash gas loss region of an evaporator thereby increasing the efficiency and heating capacity of a heat pump.
And still another objective of the present invention is to provide an evaporator low pressure, suction side to liquid refrigerant heat exchanger, and condenser system that is highly reliable in use.
Even yet another objective of the present invention is to provide an evaporator, low pressure, suction side to liquid refrigerant heat exchanger, and condenser system having an increased Energy Efficiency Ratio (EER) as a result of increased refrigeration capacity at a relatively small increase in wattage input.
Yet another objective of the present invention is to overcome evaporator design deficiencies whereby the warmer superheat region and flash gas loss region are located downstream in the air flow direction from the colder phase change region of the evaporator by reducing or eliminating these warmer regions.
And still another objective of the present invention is to provide an apparatus and method that will increase the heating capacity of heat pump systems by increasing the effectiveness of the evaporator while reclaiming the heat normally lost by the liquid refrigerant in the flash gas loss region of the outdoor coil of a heat pump operating in the heat pump mode.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure.
Accordingly, other objects and a more comprehensive understanding of the invention may be obtained by referring to the summary of the invention, and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.
The present invention is defined by the appended claims with the specific embodiment shown in the attached drawings. The present invention is directed to an apparatus and system that satisfies the need for increased refrigeration capacity in any kind of refrigeration system and increased dehumidification in air cooling systems as well as increased capacity and efficiency of any type of heat producing heat pump refrigeration system.
For the purpose of summarizing the invention, the low pressure, suction side refrigerant to liquid refrigerant heat exchanger system, for reducing or eliminating flash gas loss and superheat regions of an evaporator and reclaiming liquid refrigerant flash gas loss heat, comprises a low pressure side to liquid refrigerant heat exchanger with the low pressure gas side of the heat exchanger located downstream of the refrigeration systems evaporator, yet upstream of the sensing bulb or sensor of the refrigeration systems thermostatic expansion valve and the liquid side of the heat exchanger located upstream of the thermostatic expansion valve.
Simply, the liquid refrigerant passing through the liquid side of the heat exchanger is cooled by the evaporating and superheating refrigerant passing through the low-pressure side of the heat exchanger. The present invention providing maximum subcooling to the liquid refrigerant yet not exceeding the superheat setting of the TXV.
Moreover, the present invention provides such a cold liquid refrigerant to the TXV that flash gas loss in the evaporator is minimized or eliminated thereby increasing the effective evaporator surface area. Also, the superheat region of the evaporator is eliminated by the present invention so that the effective evaporator surface area is increased even more. Because of the increased effective surface area of the evaporator, a significant increase in refrigerant mass flow through the evaporator is accomplished thereby increasing the refrigeration capacity of the system.
Further, where heating is the primary function of the refrigeration system, such as in a heat pump heating cycle, the heating capacity is increased both by the improved heat absorption capacity of the evaporator as well as by the heat reclaim of liquid refrigerant heat in the low pressure, suction side to liquid refrigerant heat exchanger.
An important feature of the present invention is that the increased mass flow of refrigerant through the evaporator also increases the volumetric efficiency of the compressor, thereby increasing the overall system efficiency.
The foregoing has outlined rather broadly, the more pertinent and important features of the present invention. The detailed description of the invention that follows is offered so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter. These form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the disclosed specific embodiment may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.